Patterning sub-25nm hp hexagonal arrays of contact ...

PATTERNING SUB-25 NM HP HEXAGONAL ARRAYS OF CONTACT HOLES WITH CHEMO-EPITAXIAL DSA GUIDED BY ArFi PRE-PATTERNS ARJUN SINGH, BT CHAN & ROEL GRONHEID

DONI PARNEL

HENGPENG WU, JIAN YIN & YI CAO 25/02/2015 9425-34

OUTLINE I.

II.

III.

IV.

Introduction •

Chemoepitaxy of cylinders and limitations of previous work

•

CHIPS flow overview

Making pre-patterns for CHIPS •

Photolithography setup

•

Trim etch

DSA •

15 nm hp and 22.5 nm hp BCP assembly

•

Effect of brush composition

•

Impact of pre-pattern dimensions

Summary and outlook

ARJUN SINGH - SPIE AL 2015 9425-34

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CHEMOEPITAXY OF CYLINDERS PS PMMA

• Hexagonally packed cylinders in bulk & thin film PS-b-PMMA

•

DSA of cylinders using chemo-epitaxy first reported by Ruiz et al (Science, 2008)

•

We demonstrated a scaled up version using EUVL on 300 mm wafers called the HONEYCOMB flow (Proc. SPIE, 2013 & 2014)

•

“Background-first” approach in all cases – high PS affinity under-layer selectively modified with plasma etch to make PMMA wetting spots

• Asymmetric di-block BCP • PS volume fraction ≈ 0.7 to 0.8 ARJUN SINGH - SPIE AL 2015 9425-34

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LIMITATIONS OF THE BG-FIRST APPROACH •

Limited control of pre-pattern spot chemistry Polar guiding spots; DSA of PS (or other lower polarity) cylinder forming BCPs not possible



•

Scaling limited to > 20 nm hp without EUVL Size of pre-pattern < pitch of BCP, CD limit of ArFi hole patterning > 40 nm



•

No effective shrink solution for pre-pattern spot size reduction Known shrink solutions also modify the under-layer



BCP cylinder Guide spot



   

ARJUN SINGH - SPIE AL 2015 9425-34

HONEYCOMB 4x multiplication DSA of a 30 nm pitch BCP (Singh et al, Proc. SPIE 2014) 4

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CHIPS FLOW CHEMO-EPITAXY INDUCED BY PILLAR STRUCTURES

Not drawn to scale!

“Guide first” approach with pillars and back-fill brush

Litho/etch stack

Coat/graft/rinse brush

Coat X-PMMA & PTD photoresist

Strip remaining photoresist

Pattern pillars in hex. array

Trim pillars & X-PMMA with plasma etch

 Trim etch enables scaling beyond 20 nm hp  Mat pillars allow DSA of any cylindrical phase BCP Coat/anneal BCP and etch PMMA ARJUN SINGH - SPIE AL 2015 9425-34

Patent pending 5

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OUTLINE I.

II.

III.

IV.

Introduction •

Chemoepitaxy of cylinders and limitations of previous work

•

CHIPS flow overview

Making pre-patterns for CHIPS •

Photolithography setup

•

Trim etch

DSA •

15 nm hp and 22.5 nm hp BCP assembly

•

Effect of brush composition

•

Impact of pre-pattern dimensions

Summary and outlook

ARJUN SINGH - SPIE AL 2015 9425-34

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© IMEC 2015

DOUBLE LINE EXPOSURE SCHEME Phex

PLS Photoresist

•

Hexagonal arrays are printed with double line exposures (horizontal + 60 degree)

•

90 nm pitch hexagonal array (Phex) is printed with 78 nm pitch line exposures (PLS)

•

Line exposures are used for the high resolution of dipole illumination

•

Single exposure setup with SMO in development

PLS

Phex = 2PLS/ 3 ARJUN SINGH - SPIE AL 2015 9425-34

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EXPOSURE SCHEME WAFER MAP Horizontal exposure dose (mJ/cm2) 4.5

60º exposure dose (mJ/cm2)

4.5

13

21.5

Very asymmetric dose

•

Horizontal exposure vs. 60º exposure matrix

•

13±0.5 mJ/cm2 dose and nominal best focus for both exposures

•

Pillar CD decreases from top left to bottom right

13

21.5

Very asymmetric dose ARJUN SINGH - SPIE AL 2015 9425-34

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PHOTORESIST & X-PMMA TRIM Horizontal exposure dose (mJ/cm2) 4.5

13

21. 5

4.5

60º exposure dose (mJ/cm2)

Trim

13

Trim

Trim

Trim

•

Trim etch shrinks resist patterns across wafer

•

Symmetric doses yield the desired rounded pillars after trim etch

Trim

21.5

ARJUN SINGH - SPIE AL 2015 9425-34

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OUTLINE I.

II.

Introduction •

Chemoepitaxy of cylinders and limitations of previous work

•

CHIPS flow overview

Making pre-patterns for CHIPS •

Photolithography setup

•

Trim etch

III. DSA

IV.

•

15 nm hp and 22.5 nm hp BCP assembly

•

Effect of brush composition

•

Impact of pre-pattern dimensions

Summary and outlook

ARJUN SINGH - SPIE AL 2015 9425-34

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© IMEC 2015

4x FREQUENCY MULTIPLICATION

Post-trim 45 nm half-pitch

ARJUN SINGH - SPIE AL 2015 9425-34

Post-DSA 22.5 nm half-pitch AZEMBLY PME-825 Avg. CD = 23.3 nm 3σ LCDU = 4.8 nm 11

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4x FREQ. MULTIPLICATION SCHEME Phex

PBCP

•

BCP with center-to-center pitch PBCP = 45nm assembled on a hexagonal pre-pattern array with center-to-center pitch Phex = 90nm

•

Post DSA pattern frequency increase by 4x and pitch division by 2x

PBCP = Phex/2

ARJUN SINGH - SPIE AL 2015 9425-34

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4x FREQ. MULTIPLICATION WITH ORTHOGONAL PRE-PATTERNS PBCP

PLSx

PLSy

•

•

BCP with center-to-center pitch PBCP = 45 nm assembled on an othogonal pre-pattern array 

Pitch along the x axis PLSx = 90 nm



Pitch along the y axis PLSy = 78 nm

Pattern frequency increases by 4x post DSA

PBCP = PLSx/2 = √3PLSy/2 ARJUN SINGH - SPIE AL 2015 9425-34

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HEXAGONAL VS. ORTHOGONAL PRE-PATTERN Hexagonal pre-pattern • 90 nm pitch • Elliptical pillars with double line exposures

Orthogonal pre-pattern • 90/78 nm pitch • Rounded pillars with double line exposures

Litho ARJUN SINGH - SPIE AL 2015 9425-34

Trim

DSA 22.5 nm hp 4x freq. mul. 14

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9x FREQUENCY MULTIPLICATION

Post-trim 45 nm half-pitch

ARJUN SINGH - SPIE AL 2015 9425-34

Post-DSA 15 nm half-pitch AZEMBLY PME-633 Avg. CD = 14.8 nm 3σ LCDU = 2.8 nm

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9x FREQ. MULTIPLICATION SCHEME Phex

PBCP •

BCP with center-to-center pitch PBCP = 45 nm assembled on a hexagonal pre-pattern array with center-to-center pitch Phex = 90 nm

•

Post DSA pattern frequency increase by 9x and pitch division by 3x

PBCP = Phex/3 ARJUN SINGH - SPIE AL 2015 9425-34

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EFFECT OF PRE-PATTERN SIZE Trim

DSA

Mixed morphology ARJUN SINGH - SPIE AL 2015 9425-34

Perpendicular assembly with freq. mul.

Perpendicular assembly in multiple grains 17

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PROCESS WINDOW DEFINITION Horizontal exposure dose (mJ/cm2) 4.5

13

21.5

60º exposure dose (mJ/cm2)

4.5

13

•

965 fields – One 180kx magnification image per field evaluated qualitatively

•

Green fields – good assembly (1 grain, 0 visible defects)

•

Process window is defined as ∆ 𝑑𝑜𝑠𝑒 𝑠𝑦𝑚𝑚𝑒𝑡𝑟𝑖𝑐 𝑑𝑜𝑠𝑒 𝑎𝑡 𝑐𝑒𝑛𝑡𝑒𝑟 𝑜𝑓 𝑎𝑠𝑠𝑒𝑚𝑏𝑙𝑦 𝑤𝑖𝑛𝑑𝑜𝑤

For this example, 𝑃𝑊 =

4.5 = 28% 16

21.5

ARJUN SINGH - SPIE AL 2015 9425-34

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IMPACT OF BRUSH COMPOSITION 4x ≈ 32% brush wet by PMMA domains

13% PW

23% PW

20% PW

10% PW

Increasing PMMA affinity 9x ≈ 38% brush wet by PMMA domains

13% PW

28% PW

28% PW

22% PW

•

Brush must provide a non-preferential wetting interface to PS and PMMA domains not on guide spots

•

PW shifts to higher PMMA affinity brush for 9x

•

In line with 4x freq. multi. results from the HONEYCOMB flow (Singh et al, Proc. SPIE 2014)

•

Similar calculations/results for the LiNe flow reported by Liu, Nealey, et al (Macromolecules, 2013) ARJUN SINGH - SPIE AL 2015 9425-34

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SUMMARY •

Enabled sub-25 nm hp patterning of dense hexagonal arrays of holes/pillars with ArFi and DSA

•

Demonstrated scalability to 15 nm hp and frequency multiplication factors > 4x

•

Established the impact of brush composition on process windows for 4x and 9x

•

Potential applications are technologies requiring high density of 2D features, especially memory (DRAM, eDRAM, etc.)

ARJUN SINGH - SPIE AL 2015 9425-34

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ACKNOWLEDGEMENT Geert Vandenberghe Joost Bekaert Koen D’have Paulina Rincon-Delgadillo

Robert Seidel Lance Williamson

ARJUN SINGH - SPIE AL 2015 9425-34

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POST TRIM IMAGES ACROSS PW

9x multiplication PME-633 on NLD-328

ARJUN SINGH - SPIE AL 2015 9425-34

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Asymmetric dose combinations exaggerate the X/Y aspect ratio of the pillars

•

Perfectly round pre-patterns are not necessary for guiding perpendicular assembly of cylindrical domains

•

CD measurements after trim are challenging because of poor contrast in SEM images

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